This invention relates in general to magnetic tumbler locks of the type using a coded magnetic key to operate in concert a plurality of individual magnetic tumblers.
Prior art magnetic locks of this type have employed a magnetic repulsion force to effect the movement of the tumblers for unlocking the cylinders. In such devices the magnetic tumbler elements and the biasing springs therefore are mounted in the outer lock cylinder for selective engagement and locking with cooperating detents formed in the inner cylinder. When the magnetic key is inserted in the inner cylinder keyway, the tumblers carried in the outer cylinder are magnetically repulsed and thus displaced from the inner cylinder detents to allow rotation of the inner cylinder and key.
Devices of this type have been found very useful and have proven to be satisfactory in most all respects. However, there are some lock applications which require a more positive, reliable magnetic inner action between the coded magnetic key and the individual tumblers. Additionally, in some cases excessive wear occurs in the prior devices which operate on a magnetic repulsion principle, because once the tumblers are repulsed and released from the inner cylinder detents, rotation of the key to open the lock disrupts the magnetic repulsion force and causes the tumblers to be forced under spring bias into abrasive engagement with the inner rotating cylinder. This causes undesirable wear on the outer circumference of the inner cylinder and leads to a shortened useful life of the lock.
Positioning the spring-biased tumblers, including the biasing spring assembly in the outer lock cylinder, also increases the overall size of the lock. In most cases, the tumbler and biasing spring are arranged so as to be radially aligned with the magnetic elements of the key so that the tumblers are repulsed along a radial line with respect to the cylinders. This usual radial alignment requires that the outer locking cylinder have relatively large cross-sectional dimensions at least in the region of the tumblers to accommodate this radial tumbler motion. It would be desirable to provide a more compact lock mechanism, however the nature of the magnetic repulsion used by prior art locks of this type necessitates the larger construction.
Accordingly it is an object of the present invention to provide a magnetic tumbler lock which is an improvement over the existing, prior art magnetic locks and eliminates one or more of the above noted disadvantages thereof. More particularly, it is one object of the present invention to provide a more reliable positive locking and unlocking action by enhancing the magnetic forces which interact between the magnetically coded key and plurality of magnetic tumblers.
Another object of the present invention is to provide a more compact lock construction, in which the overall size of the inner and outer cylinders is reduced.
Still a further object of the present invention is to provide a lock mechanism of the magnetic tumbler type capable of providing improved lock security in terms of the number and orientation of the magnetic elements carried by the key and the sensitivity of the magnetic tumblers thereto.
Additionally, it is an object of the present invention to eliminate the mechanical wear on the tumblers as encountered in prior art devices in which the tumblers are released after rotating the key so as to forcefully engage the rotating inner cylinder under the urging of the spring bias.
In general these objectives are achieved in the present invention by a key operated magnetic tumbler lock construction in which the magnetic tumblers are mounted inside the inner cylinder in side-by-side relation to the keyway therein with the magnetic poles of the tumblers oriented with respect to the magnetic elements of the key so as to cause mutual magnetic attraction therebetween. The tumblers are thus normally urged by biasing springs also carried by the inner cylinder into a protracted condition with respect thereto so as to engage cooperating detents formed in the outer cylinder. Insertion of the magnetically coded key causes the tumblers to be magnetically attracted, under a stronger and more positive magnetic force than available from magnetic repulsion, into a retracted condition relative to the inner cylinder to allow the key and inner cylinder to rotate. This results in a more compact arrangement because the tumblers are mounted in space efficient side-by-side relation with the keyway inside the inner cylinder. Additionally, since the tumblers are displaced by magnetic attraction rather than repulsion, they continue to be held in a retracted or recessed relationship with respect to the outer cylinder detents while the inner cylinder is being rotated by the key to the unlocked position. No mechanical wear is incurred by the tumblers because they are held out of engagement from the inner surface of the outer cylinder during the unlocking rotation.
In one of the embodiments of the invention as disclosed herein, the magnetic attraction between the tumblers and coded key is employed to provide a locking device having enhanced security. Briefly this is achieved by taking advantage of the fact that each of the tumbler magnets and the associated key magnets tend to be attracted into a stable magnetic relationship in which the magnets are substantially in juxtaposition. This is an automatic positioning principle which is used to selectively position a plurality of double-ended tumblers which are disposed to protrude from either of substantially opposite portions of the inner cylinder to engage opposed detents on the inner wall of the outer cylinder. The double-ended tumbler must be positioned so as not to protrude at either end from the inner cylinder in order to unlock the device, and this positioning is achieved by using the self-seeking alignment of the magnetic attraction forces.
These and further objects, features and advantages of the key operated magnetic tumbler lock in accordance with the present invention will become apparent to those skilled in the art from a consideration of the following detailed description and accompanying drawings of the preferred embodiments of the invention.